Animal Core- The responsibilities of the Animal Core are 5-fold: (1) To coordinate the purchase and numbering of young and aged rats and monkeys for all four Projects; (2) To train rats and monkeys on the appropriate cognitive tasks (Projects 1, 2 and 4); (3) To perform neural implant aseptic surgeries for monkeys used in electrophysiological studies (Project 1), and rats receiving viral transfections in prefrontal cortex (Project 2); (4) To perform cognitive assessment of rats (Projects 2 and 4) and monkeys (Project 4) in order to evaluate the effects of viral transfection or chronic drug treatment; and (5) To assist with chronic drug treatment (Project 4). Cognitive testing will include several tests of spatial working memory. For Project 1, young and aged monkeys will be habituated to sitting in a primate chair while interacting with a computer monitor. They will then be trained on the oculomotor spatial delayed response task. Training aged monkeys to perform this task requires patience, but is feasible if done gradually. Projects 2 and 4 will require training of young and aged rats on the spatial delayed alternation task in a T maze. A separate group of rats will also be trained on a control task, spatial discrimination, in the same T maze, to examine the specificity of viral manipulations in prefrontal cortex on cognitive function. Finally, young and aged monkeys in Project 4 will be trained and tested on spatial delayed response in a Wisconsin General Test Apparatus, a classical test of dorsolateral prefrontal cortical function. Animals in chronic drug studies will be tested twice weekly. The experimenter testing the animals will be unware of the drug or viral treatment conditions. Cognitive data will be submitted to the Administrative Core for statistical analysis, to examine the relationships between cognitive, histological and /or biochemical data. LAY SUMMARY: The Animal Core will train and test young and aged animals on memory tasks. We will see if drugs or molecular manipulations in the brain of rats will slow the aging process and improve memory.